As a manufacturer, Ideal Plastic provides high-performance Vespel SP-21 Rods. SP-21 polyimide rod is a classic modified polyimide composite formulated with 15% graphite filling. This moderate graphite ratio perfectly balances the pure PI’s high mechanical strength and graphite’s self-lubricating advantage, avoiding the strength attenuation of high-filler grades and the poor wear resistance of unfilled PI. With a specific gravity of 1.51g/cm³, the material retains the non-melting thermosetting characteristics of standard polyimide, delivering continuous structural stability at 260°C+ long-term operating temperatures.
Frictional characteristics
During friction operation, the layered graphite structure forms a uniform protective transfer film on the contact surface, effectively reducing adhesive wear and maintaining a stable friction coefficient of approximately 0.3. Its thermal expansion performance is superior to pure polyimide and slightly higher than high-graphite SP-22 grades, making it ideal for universal precision wearable parts that require both mechanical rigidity and anti-friction durability.
Molding Process and Production Compatibility
Adopting standard compression molding technology, our SP-21 rods are manufactured with DuPont standard-grade resin powder raw materials. High-temperature and high-pressure integral molding ensures uniform internal density, low residual stress, and consistent dimensional accuracy across batches. The mature molding process supports both small-batch prototype production and large-volume standardized orders with stable cycle efficiency.
Products Data
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Product name
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Vespel SP-21 Rods
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Material
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Add 15% graphite filler specification
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Color
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black
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Dia
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5-150mm
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Length
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1000mm
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Tolerance
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±0.02mm
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sample
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Negotiation
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Minimum order quantity
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1 piece
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Certificates
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ISO9001:2008, REACH, ROHS
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Additional services
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Secondary processing can be provided.
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Core Functional Characteristics of 15% Graphite Modified PI
1. Ultra-Wide Temperature Adaptability
SP-21 features extreme temperature resistance covering cryogenic to high-temperature scenarios. It operates stably from -196°C low-temperature environment to 288°C long-term continuous working condition, and withstands short-term instantaneous high temperature up to 480°C. No structural cracking, strength attenuation or dimensional deformation occurs under extreme temperature alternation, fully meeting the stringent temperature resistance requirements of precision industrial equipment.
2. Controlled Low Thermal Shrinkage & Precision Stability
The material owns a stable thermal expansion coefficient ranging from 2×10⁻⁵/°C to 3×10⁻⁵/°C, with optimal linear expansion as low as 3×10⁻⁶/°C. The moderate graphite filling effectively inhibits thermal shrinkage and expansion compared with pure polyimide, ensuring consistent dimensional accuracy of precision transmission parts during long-term temperature fluctuation cycles.
3. Balanced Mechanical Rigidity & Creep Resistance
Balanced formula design endows SP-21 with reliable mechanical properties: tensile strength reaches 95 MPa and flexural strength is 128 MPa at room temperature (23°C). Though slightly lower in tensile strength than unfilled SP-1 pure PI, it achieves higher surface hardness and superior high-temperature creep resistance. It maintains stable structural rigidity under long-term sustained load, effectively avoiding permanent deformation of moving parts.
4. Inherent Flame Retardant Safety
Relying on stable aromatic heterocyclic molecular structure, SP-21 possesses natural flame retardant performance. When exposed to open fire, the surface rapidly forms a dense carbonized insulation layer to isolate oxygen and block heat transfer. Meanwhile, it decomposes and releases inert gases such as CO₂ and N₂ to dilute ambient oxygen, achieving self-extinguishing effect without additional flame retardant additives, compliant with industrial safety standards.
5. Full-Temperature Stable Self-Lubricating Performance
Different from ordinary lubricating plastics with temperature-sensitive friction coefficient, SP-21 maintains consistent self-lubricating performance in the ultra-wide temperature range of -269°C to 330°C. The friction coefficient fluctuates no more than 15% even under continuous high-temperature friction, ensuring stable operation of high-speed moving parts without dry-grinding failure.
6. Excellent Hydrolysis & Steam Corrosion Resistance
Vespel SP-21 Rods exhibit outstanding hot water and steam aging resistance. It can withstand 500-hour continuous boiling test at 120°C and 2 atmospheric pressure environments, retaining complete mechanical strength without hydrolysis degradation. It stays stable in high-temperature steam and conventional dilute chemical media, suitable for humid and thermal cycle working scenarios.
Material Strengths & Practical Application Constraints
Core Competitive Strengths
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15% moderate graphite formula realizes perfect balance of mechanical strength and self-lubrication, more versatile than pure PI and high-graphite PI grades
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Ultra-wide temperature adaptability from cryogenic to high-temperature, supporting full-scene industrial continuous operation
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Stable low friction coefficient and anti-wear performance, reducing part wear rate and equipment maintenance frequency
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Excellent high-temperature creep resistance and low thermal shrinkage, ensuring long-term precision stability of transmission parts
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Natural flame retardant, hydrolysis resistance and steam corrosion resistance, adaptable to harsh working environments
Practical Application Limitations
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Thermal dimensional stability is inferior to 40% high-graphite SP-22 grade, not suitable for ultra-high precision parts requiring zero deformation under extreme temperature difference
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Lacks PTFE component, its extreme dry friction performance is slightly lower than SP-211 dual-filler grade
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Graphite filler leads to weak conductive property, not applicable for ultra-high insulation electronic component scenarios
Material Grade Comparison: SP-21 VS mainstream PI & Engineering Plastics
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Comparison Item
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SP-21 (15% Graphite PI)
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SP-22 (40% Graphite PI)
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SP-211 (Graphite+PTFE PI)
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Unfilled Pure PI
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PEEK
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Filler Feature
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15% moderate graphite, balanced performance
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40% high graphite, ultra-stable dimension
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Graphite+PTFE, extreme low friction
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No filler, highest strength
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Mechanical comprehensive optimization
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Thermal Stability
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Good
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Excellent (top-tier)
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Very Good
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Medium
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Medium
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Self-Lubricating & Wear Resistance
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Balanced & stable
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Good
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Excellent
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Average
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Good
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Mechanical Strength
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High
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Medium-High
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Medium
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Highest
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High
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Best Application Scenarios
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Universal wearable transmission parts
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Ultra-precision zero-deformation parts
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Heavy-load dry friction parts
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High-strength insulating parts
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General structural parts
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Industrial Application Scenarios
Tailored for universal high-temperature, high-wear and long-cycle operating conditions, Vespel SP-21 Rods are widely machined into wearable transmission components for multiple industrial fields:
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Petrochemical Industry: High-temperature resistant sealing parts, wear-resistant bearing components for oil and gas transmission equipment
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Communication Equipment: Precision wearable structural parts, high-temperature stable insulating accessories
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Chemical Industry: Steam corrosion resistant parts, medium-contact wearable components
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Semiconductor Industry: High-temperature processing fixture accessories, low-deformation transmission parts
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Automotive Industry: Engine high-temperature wearable parts, thrust washers, piston rings and bearing seals
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Construction Machinery: High-load cyclic moving gears, wear-resistant shaft sleeve components
Petrochemical Industry
Communication Equipment
Chemical Industry
Semiconductor Industry
Automotive Industry
Construction Machinery
Precision Machining & Customized Industrial Solutions
We provide one-stop customized service for SP-21 polyimide products, covering standard rod supply and finished precision parts processing. Support full-format drawing customization, physical sample reverse engineering, 4/5-axis CNC precision milling, laser cutting and fine surface polishing. All processed parts reach assembly-level precision, adapting to diverse industrial equipment assembly standards and eliminating secondary calibration costs for customers.
Factory Technical & Production Advantages
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Professional PI Forming Experience: 14+ years of specialized production experience in modified polyimide materials, proficient in formula control and compression molding process of 15% graphite-filled SP-21 grade
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Standard Raw Material Adoption: Adopts industry-standard Vespel-grade polyimide resin powder, strictly controlling filler proportion to ensure consistent balanced performance of each batch of products
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Efficient Compression Molding Process: Optimized high-temperature and high-pressure molding technology ensures uniform internal density, stable mechanical properties and short production cycle, supporting mass standardized orders
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Complete R&D & Testing System: Equipped with professional performance testing instruments, providing accurate material test reports and full-process technical support for customer project verification
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Senior Technical Team Support: Dedicated R&D team and experienced production technicians control product quality from formula, molding to finished product inspection
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Global Service & Delivery Capacity: Serves thousands of global industrial customers, with mature production and supply system to meet small-batch trial production and large-scale batch procurement demands
Product & Service Advantages
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Balanced Performance Formula: Stable 15% graphite filling ratio balances strength and wear resistance, solving the single performance defect of pure PI and high-filler PI materials
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Stable Batch Consistency: Standardized molding process eliminates residual internal stress, ensuring consistent dimensional and mechanical properties across different batches
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Wide Working Condition Adaptability: Supports ultra-wide temperature operation and harsh environments such as steam and chemical medium corrosion, with high comprehensive applicability
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Low-Cost Industrial Matching: Cost-effective compared with high-grade SP-22/SP-211, ideal for mass replacement of wearable parts to reduce overall equipment operating costs
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Flexible Custom Service: 1-piece MOQ supports prototype testing and small-batch trial production, with full-link CNC customized processing to meet personalized part requirements
FAQ
1. What raw‑material source and molding technology are adopted for your Vespel SP‑21 rod blanks?
Our SP‑21 polyimide rods are compression‑molded from genuine DuPont Vespel SP‑21 resin powder under high heat and pressure. This powder‑compression manufacturing route delivers uniform internal density and stable dimensional consistency, making it well‑suited for medium‑to‑large volume production runs.
2. What is the composition, color and density specification of SP‑21?
This grade incorporates 15 % graphite as solid lubricant filler, presenting a black appearance, with specific gravity reaching 1.51 g/cm³.
3. What temperature spectrum can SP‑21 continuously withstand?
It maintains structural strength above 260 °C under long‑term operating conditions. Its usable working window spans ‑196 °C up to 288 °C, while short‑time peak exposure can tolerate temperatures as high as 480 °C.
4. What are key mechanical indices measured at room temperature of 23 °C?
At ambient 23 °C testing condition: tensile strength hits 95 MPa, flexural strength reaches 128 MPa, and heat‑deflection temperature exceeds 360 °C. Compared to unfilled SP‑1, SP‑21 trades partial tensile performance for higher hardness and better stress‑resisting creep behaviour.
5. How does graphite filler influence SP‑21 friction performance across temperature ranges?
The embedded graphite generates a protective transfer film upon contact‑surface rubbing, bringing an approximate friction coefficient of 0.3. Its self‑lubricating property remains stable across an ultra‑wide span from ‑269 °C to 330 °C; friction coefficient fluctuation stays within 15 % even under sustained high‑temperature working conditions. This material supports high pV working values and performs reliably under dry‑run high‑friction scenarios.
6. How about thermal expansion feature compared to other Vespel grades?
Its thermal expansion coefficient falls within 2×10⁻⁵ /°C ~ 3×10⁻⁵ /°C, with minimum achievable linear expansion down to 3×10⁻⁶ /°C. Thermally‑induced dimensional shift is lower than non‑filled pure PI, yet moderately higher than heavy‑graphite modified SP‑22. Such property satisfies the dimensional accuracy requirements of precision instrument components.
7. What special inherent material traits does SP‑21 possess?
Intrinsic flame retardancy: a charred isolating layer forms over surfaces during combustion, releasing inert gas to suppress flame spread.
Outstanding hydrolysis resistance: maintains mechanical integrity after 500‑hour exposure to 120 °C pressurized boiling steam at 2 atm, resisting high‑temperature steam degradation.
Superior anti‑creep capacity when subjected to persistent mechanical stress.
8. Which components and industries commonly apply SP‑21 graphite‑filled polyimide?
Machined parts include thrust washers, piston rings, transmission gears and multi‑form bearing sealing elements. Typical downstream sectors cover petrochemical processing, general chemical plants, communication hardware, semiconductor manufacturing, automotive parts and construction machinery.
9. What stock dimensions and tolerance level can you supply?
Available rod diameter covers 5‑150 mm; standard factory length is 1000 mm, with dimensional tolerance controlled at ±0.02 mm.
10. How do you handle order quantities for blanks and custom‑machined finished parts?
We accept orders starting from 1 piece for semi‑finished SP‑21 rod blanks. For fully finished custom‑machined components, minimum quantity will be individually evaluated according to part geometry and processing complexity.
11. Can you process parts based on customer drawings or physical samples?
Secondary manufacturing services are available. We support mainstream drawing file formats such as STEP, STP, STL, IGS, IGES, PRT, SLDPRT, SAT and X‑T. We can also reverse‑engineer and produce parts directly from customer‑supplied physical samples.
12. Which compliance certificates accompany SP‑21 rod products?
Our Vespel SP-21 Rods pass ISO9001:2008 quality management system audit, together with SGS and CE testing. They satisfy RoHS, REACH and EN71 international environmental compliance requirements.
13. Is sample evaluation accessible for performance qualification?
Complimentary sample blanks can be offered for items held in stock; customers take charge of delivery freight. Mass‑produced goods keep identical performance standard as qualification samples; sample availability needs case‑by‑case confirmation.
14. What is your commercial payment workflow?
Production gets started after receiving pre‑production deposit. Full remaining balance should be settled once goods finish manufacturing. We trigger shipment upon receipt of final payment. Payment options include remittance to our Hong‑Kong‑based HSBC account or settlement via your nominated freight forwarder.
15. How is production lead‑time determined?
In‑stock rod blanks can be dispatched right after payment confirmation. Lead‑time for non‑standard custom orders depends on batch volume and process comple
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